26. This is the maximum because this was the oldest age tested in clinical studies. While the vaccine is theoretically safe in other age groups we cannot say so without specifically testing it. So the age restriction remains until that is done.

Targeting . When drug companies bring a drug to the FDA for approval they must have data on any age groups that they seek approval.That takes time and money. It took 2+ decades and millions of dollars to bring this to market. It is likely the vaccine works for anyone with an intact immune system at any age. Use outside of the approved target is rarely covered by insurers,and subjects the doc to extra scruteny.

26 yo. The hpv vaccines are recommended for women and men between the ages of 9-26. It is not recommended for people over 26 because research has not demonstrated the vaccines to be effective for these individuals. The vaccines work best when given at ages 11 or 12 before initiation of sexual activity and because the vaccine produces higher antibody that fights infection when given at these ages.